The present invention relates to a photothermographic material.
Recently, in a medical treatment diagnosis film field and a photomechanical film field, from the viewpoints of the environmental safety and the space saving, the reduction of the amount of the processing waste liquids has been strongly demanded. Thus, the technique about photothermographic materials as a medical treatment diagnosis film and a photomechanical film, which can be efficiently exposed by a laser image setter or a laser imager and can form clear black images having a high resolution and a high sharpness, has been required. According to these photothermographic materials, solution-type processing chemicals are not required, and a heat-development processing system, which is simpler and does not spoil the environment, can be provided to customers.
In general image-forming material field, there is the same requirement, but in particular, because the images for the medical treatment diagnosis are required to have minute depictions, images having excellent sharpness and graininess are necessary and it is preferred to have images in a blue black tone from the view point of ease of diagnosis. At present, various hard copy systems utilizing pigments, dyes, etc., such as an ink jet printer, an electrophotography, etc., have been mainly used as general image-forming systems but there are no systems, which can be satisfactorily used as an output system for medical treatment systems.
On the other hand, thermal image forming systems utilizing organic silver salts are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075; D. Klosterboer, Thermally processed Silver Systems (Imaging Processes and Material), Neblette, the 8th edition, J. Sturge, V. Walworth, and A. Shepp edited, Chapter 9, page 279, 1989). In particular, a photothermographic material generally has a light-sensitive layer containing photocatalyst of a catalytic-active amount (for example, a silver halide), a reducing agent, a reducible silver salt (for example, an organic silver salt), and, if necessary, a color toning agent of controlling the color tone of silver, dispersed in a binder matrix. The photothermographic material is, after imagewise exposure, heated to a high temperature (for example, at least 80xc2x0 C.) and forms black silver images by the redox reaction between the reducible silver salt (functions as an oxidizing agent) and the reducing agent. The redox reaction is accelerated by the catalytic action of the latent image of the silver halide generated by the light exposure. Thus, the black silver image is formed in the light-exposed region. They are disclosed in many literatures such as U.S. Pat. No. 2,910,377, JP-B-43-4924 (The term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d), etc.
On the other hand, for producing the photothermographic materials at a high speed and stably, it is important to control the properties of the coating solution with a surface active agent. As the problems for the production, there are the problems of the coating properties such as repelling and face roughening and the problems by attaching of foreign matters such as dust, etc. In these problems, it is described in JP-A-10-197985 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) that a fluorine-based surface active agent is effective for the improvement of the occurrence of repelling and face roughening. However, about the problem of attaching of foreign matters such as dust, etc., the improvement is not in the sufficiently satisfying level.
The present invention serves to solve the problems of the conventional techniques described above. That is, the present invention provides a photothermographic material excellent in the heat-developing property and image stock stability, which prevents the attachment of foreign matters such as dust, etc., causing white spots (a white spot is determined by visual observance using a magnifying lens on a Shaukasten wherein the sample has a density of 2.0) after heat development.
As the result of intensively investigating the above-described problems, the present inventors have found that by using a surface active agent having a definite structure, the excellent photothermographic material giving the desired effects can be provided and have accomplished the present invention.
That is, according to the invention, a photothermographic material comprising a support having provided on one surface thereof at least one kind of a light-sensitive silver halide, a light-insensitive organic silver salt, a reducing agent for a silver ion, and a binder, wherein the photothermographic material comprises a surface active agent represented by the following formula (F) is provided, 
wherein Rf represents a perfluoroalkyl group, Rc represents an alkylene group, Z represents a group having an anionic group, a cationic group, a betaine-series group, or a nonionic polar group necessary for imparting a surface activity, n represents an integer of 0 or 1, and m represents an integer of 1, 2 or 3.
In the above-described photothermographic material, it is preferable that the reducing agent is a reducing agent represented by the following formula (I): 
wherein R1 and R1xe2x80x2 each independently represents an alkyl group having from 1 to 20 carbon atoms, R2 and R2xe2x80x2 each independently represents a hydrogen atom, or a substituent capable of being substituted to the benzene ring, L represents an xe2x80x94Sxe2x80x94 group or a xe2x80x94CHR3xe2x80x94 group, wherein R3 represents a hydrogen atom or an alkyl group having from 1 to 20 carbon atoms, and X and Xxe2x80x2 each independently represents a hydrogen atom or a substituent capable of being substituted to the benzene ring.
Also, it is preferable that the photothermographic material of the invention further comprises a compound represented by the following formula (II): 
wherein R10, R11, and R12 each independently represents an alkyl group, an aralkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, or a heterocyclic group.
It is preferable that the photothermographic material of the invention further comprises a compound represented by the following formula (III):
Qxe2x80x94(Y)nxe2x80x94C(Z1)(Z2)Xxe2x80x83xe2x80x83(III)
wherein Q represents an alkyl group, an aryl group, or a heterocyclic group, Y represents a divalent connecting group, n represents 0 or 1, Z1 and Z2 each represents a halogen atom, and X represents a hydrogen atom or an electron attractive group.